This invention relates to a hot gas engine of the type comprising a first piston adapted to reciprocate in a first cylinder which is kept at a lower temperature level and a second piston adapted to reciprocate in a second cylinder which is kept at a higher temperature level, the said two pistons forming walls of an enclosure containing a working gas charge, said enclosure also comprising a cooler, a regenerator and a heater.
It is well known to control the power output of a hot gas engine by adjusting the amount of gas in the working gas charge. This is often done by pumping gas from said working gas charge into a gas reservoir when the power output should be decreased and by supplying gas into said working gas charge from said reservoir when the power output should be increased.
The gas pressure in the working gas charge will vary during the working cycles. Thus, the gas pressure may vary between e.g. 4 and 8 MPa at low power outputs and between 12 and 20 MPa at higher power outputs. In order to expose the compressor piston seals to smaller differential pressures it is most advantageous to install the compressor inside the engine so that any leakage will be at a relative high pressure i.e. at least the lowest of the practically occurring working gas pressures. However, when the compressor is arranged in a low temperature part of the engine the compressor parts of prior art construction have been inaccessible and therefore very difficult to inspect and service.